Remove error of CleverDict for negative indices (#1167)

Author: blegat

src/Utilities/CleverDicts.jl

@@ -169,8 +169,6 @@ function Base.setindex!(c::CleverDict{K, V}, value::V, key::K)::V where {K, V}
     h = c.hash(key)::Int64
     if h > c.last_index
         c.last_index = ifelse(h == c.last_index + 1, h, -1)
-    elseif h <= 0
-        error("Invalid key, its hash must be > 0")
     end
     if 1 <= h <= length(c.vector) && _is_dense(c)
         c.vector[h] = value

test/Bridges/lazy_bridge_optimizer.jl

@@ -682,6 +682,21 @@ end
     MOIT.contlineartest(bridged, MOIT.TestConfig{T}(solve=false), exclude)
 end
 
+@testset "SDPAModel with bridges and caching" begin
+    # This tests that the computation of the reverse dict in the
+    # caching optimizer works with negative indices
+    cached = MOIU.CachingOptimizer(MOIU.Model{Float64}(), MOIU.MANUAL)
+    vi_cache = MOI.add_variable(cached)
+    model = SDPAModel{Float64}()
+    bridged = MOIB.full_bridge_optimizer(model, Float64)
+    MOIU.reset_optimizer(cached, bridged)
+    MOIU.attach_optimizer(cached)
+    vi_bridged = first(MOI.get(bridged, MOI.ListOfVariableIndices()))
+    @test vi_bridged == MOI.VariableIndex(-1)
+    @test cached.model_to_optimizer_map[vi_cache] == vi_bridged
+    @test cached.optimizer_to_model_map[vi_bridged] == vi_cache
+end
+
 @testset "Continuous Conic with SDPAModel{Float64}" begin
     model = SDPAModel{Float64}()
     bridged = MOIB.full_bridge_optimizer(model, Float64)